envelope

C1 · Advanced Countable noun Engineering Technical

n. the limits of what a machine or system can safely do.

n. the set of performance limits within which a technological system, especially an aircraft, can operate safely.

“The test pilot was careful not to fly outside the safety envelope.”

“By incorporating carbon-fibre components, the design team managed to push the performance envelope of the prototype significantly.”

B2 · Upper Intermediate Countable noun Science Academic

n. a layer that wraps around or covers something else.

n. a natural or artificial covering that encloses an object or structure.

“The virus is protected by an outer envelope made of proteins.”

“The building's thermal envelope was upgraded with high-performance insulation to reduce energy loss during the winter months.”

C2 · Proficiency Countable noun Music Technical

n. the way a sound changes in volume over time.

n. the variation in the amplitude of a sound signal over time, typically defined by attack, decay, sustain, and release.

“He adjusted the envelope on the synthesizer to make the notes sound softer.”

“The sound engineer manipulated the ADSR envelope to give the lead synth a more percussive, aggressive character.”

C1 · Advanced Countable noun Technical

n. the large fabric bag that holds the gas in a hot-air balloon.

n. the fabric structure of an aerostat that contains the lifting gas.

“The ground crew checked the envelope for small holes before the flight.”

“The hot-air balloon's nylon envelope expanded rapidly as the burners blasted heat into the opening.”